Place the cubed potatoes in a large pot of salted water. Bring to a boil and cook until the potatoes are tender, about 15-20 minutes.
Mash the Potatoes:
Drain the potatoes and return them to the pot. Add the milk and butter, and mash until smooth. Season with salt and pepper to taste. Cover and keep warm.
Step 2: Cook the Sausages
Brown the Sausages:
Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the sausages and cook until browned on all sides and cooked through, about 15-20 minutes. Remove the sausages from the skillet and set aside.
Step 3: Make the Caramelized Onion Gravy
Caramelize the Onions:
In the same skillet, add the butter and olive oil. Once the butter has melted, add the sliced onions and cook over medium-low heat, stirring occasionally, until the onions are golden brown and caramelized, about 20-25 minutes.
Make the Gravy:
Sprinkle the flour over the onions and stir to coat. Cook for 1-2 minutes to remove the raw flour taste. Gradually whisk in the beef broth and Worcestershire sauce. Add thyme leaves if using. Simmer until the gravy thickens, about 5-7 minutes. Season with salt and pepper to taste.
Step 4: Assemble the Dish
Plate the Dish:
Divide the mashed potatoes among plates, top with sausages, and spoon the caramelized onion gravy over the top. Serve immediately.
